Hi 

 Has anyone had any problems with pigments in PU resin loosing colour and becoming patchy over time? I am using Xencast toughened P6 with EC pigments, no fillers, mech mixed, de-gassed the parts are nice colourful and shiny when they come out the mould, after a few days the colour is dying back but the parts are still nice and glossy.

 Any help would be appreciated.

Thanks

What sort of temperature where you curing at?  How accurately is your mix measured out?

We have seen slight issues like that where the resin  (for whatever reason) has not quite fully cured off at the time of demoulding.  What tends to happen, is that it will continue to cure slightly and as it does so there is movement as  PU leeches towards the surface which can cause patchy whitening like you are seeing.

Cool temperatures can cause it,  poor mixing or poor accuracy measurement also can cause it.

Is there any greasy feel on the resin surface?  If it is only a minor imbalance or a heat issue, a light sand or polish may restore some of the finish.  

This can happen in any resin system although PU's seem a bit more cure sensitive than others and P6 is quite a sensitive resin as it is in terms of moisture, mixing etc.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant